Reclosable Packaging

ABSTRACT

The present invention is related to a flexible laminate for forming a reclosable packaging container comprising a built-in opening and reclose feature, said laminate comprising an inner structure and an outer structure, adhesively joined face-to-face, the outer structure forming the outer surface of the container and the inner structure forming the inner surface of the container, the outer structure comprising an outer flap portion delimited by a scoring line through the outer structure, and an inner structure comprising an inner flap portion delimited by a scoring line through the inner structure, the inner score line and the outer score line creating an opening into the container when the flap portions are peeled back, a marginal region of the outer flap portion extending beyond an edge of the inner flap portion and overlying an underlying surface of the inner structure, the inner and outer flap portions being joined in a second adhesive region and a first adhesive region being disposed between the marginal region of the outer flap portion and the underlying surface of the inner structure for attaching and re-attaching, in use, the outer flap portion to the underlying surface, wherein the bond/peel strength of the first adhesive region is smaller than the bond/peel strength of the second adhesive region, the first adhesive region being permanently tacky and where in the elementary chemical composition of the adhesive in the first adhesive region and the second adhesive region is substantially the same.

FIELD OF THE INVENTION

The present invention is related to reclosable packaging containers comprising a flexible laminate with a built-in opening and reclose arrangement, and to a method for the production of this flexible laminate.

STATE OF THE ART

Flexible packaging materials are used in many applications and obtained by various form fill and seal technologies using laminates of specific constitutions, generally tailor-made for their specific applications.

Flexible laminates are well known in the flexible packaging industry. The laminates are usually obtained by adhesive laminations of one or more polymer films comprising lacquers, barrier layer and metallisation layer, etc. with other possible layers such as paper, metal foils, and the like. The polymer layer may be extruded, coextruded and/or joined by permanent adhesive (PA) and/or pressure-sensitive adhesive (PSA) to the final laminate.

Flexible packages often contain products that may be used progressively over a longer period of time. If the package is not reclosable, the products are susceptible to premature aging because they are exposed to the moisture of the surrounding environment. It is therefore important to be able to correctly reclose a package after its initial opening to keep the product that remains in the package fresh.

Various built-in opening and reclose arrangements have been developed for flexible packaging containers in the last decades.

The built-in opening and reclose systems of the prior art are obtained by specific score lines performed on both sides of the flexible laminate; they delimit adhesive pattern configurations. Each of those configurations has specific advantages and drawbacks.

Nakamura discloses in EP 0 193 130 (1986) one of the first built-in opening and reclose structures in a laminate.

Alusuisse discloses in EP-A1-0 957 045 (1999) a packaging with a built-in opening and reclose flap obtained by a laminate comprising pattern-applied, permanent and pressure-sensitive adhesives in register. The laminate comprises an outer structure and an inner structure. The outer structure comprises a barrier layer. The pressure-sensitive adhesive can be positioned on the inner or outer structure. The permanent and the pressure-sensitive adhesives are both applied on the same inner or outer structure and the score lines are performed separately on the inner structure and on the outer structure of the laminate.

Alcan discloses in EP-A1-1449 789 (2004) a packaging with a built-in opening and reclose flap obtained by a laminate comprising an outer structure and an inner structure. In a first embodiment, the laminate comprises pattern-applied, permanent and pressure-sensitive adhesives in register; in a second embodiment a permanent adhesive is applied on the entire surface on the first structure of the laminate and a pattern-applied pressure-sensitive adhesive on the second structure of laminate. In this case, the permanent adhesive and the pressure-sensitive adhesives are superimposed where the PSA is pattern applied and creates a local detrimental increase of thickness entailing a deformation of the produced reel of the laminate. The disclosed outer and inner structures may comprise a series of layers, among them a barrier layer. The pressure-sensitive adhesive can be positioned on the inner or on the outer structure. The permanent adhesive and the pressure-sensitive adhesive are both applied separately on the first and second structures of the laminate. The score lines are performed separately on the inner and outer structures before the structures are joined face to face and form the laminate.

Sonoco discloses in WO 2005/123535 A1 (2005) a packaging with a built-in opening and reclose flap obtained by a laminate comprising pattern-applied, permanent and pressure-sensitive adhesives in register. The permanent adhesive does not cover the pressure-sensitive adhesive. The laminate comprises an outer structure and an inner structure, the inner structure comprises a seal layer and a barrier layer, in particular a metallized polymer layer that is able to reflect a laser beam possibly used to perform the score lines. The pressure-sensitive adhesive remains positioned on the flap after a first opening. The permanent adhesive and the pressure-sensitive adhesives are both applied in register on the same first or second structure of the laminate and the score lines are performed on the finished laminate after the inner and outer structures of the laminate are joined.

Sonoco, in a divisional application EP-A1-2 243 716 of WO 2005/123535 A1, claims the replacement of the permanent adhesive by a pressure-sensitive adhesive, wherein the first and second structures of the laminate are joined by a pressure-sensitive adhesive layer without the use of any permanent adhesive.

Wrigley in WO 2008/115693 A1 (2008) discloses a method for making a flexible built-in opening and reclose feature in a laminate comprising pattern-applied permanent adhesive and a strip of pressure-sensitive adhesive in register in the marginal region between the score lines. The laminate comprises a first structure and a second structure. The first structure is independently scored before joining the second structure and forming a laminate. The second score line is then performed on the laminate.

Printpack Illinois discloses in WO 2010/080810 A1 a reclosable container with built-in opening and reclose feature based on the inner and outer sides of a laminate with a resealable cover portion and a pressure-sensitive adhesive affixing the inner side to the outer side. Here, the basic difference compared to the mentioned prior art before 2010 is that the permanent adhesive is replaced by a heat seal.

Avery Dennison in WO 2011/032064 (2011) discloses a resealable packaging laminate with a built-in opening and reclose arrangement comprising an outer and an inner laminate portion. The outer and inner score lines being arranged to define a marginal region comprising a pressure-sensitive adhesive at least partly in contact with a release layer positioned on the inner layer.

Hochland in EP 2 347 972 A1 (2011) discloses a reclosable packaging, in particular a lid for a tray, with a built-in opening and reclose arrangement comprising a rupturable weakening line in the lid. The lid is obtained by a laminate comprising permanent adhesive in the central area of the lid and pressure-sensitive adhesive in the border area of the lid. The outer structure comprises among other possible layers a barrier layer.

Other laminates, specifically related to cigarette-pack inner or outer wrapper comprising similar built-in opening and reclose arrangements, are disclosed by BAT in WO 98/22367 and WO 2008/062159 or by Focke in WO 2011/069575 and WO 2011/110272.

Sonoco in EP 2 257 479 B1 discloses a flexible packaging laminate having built-in opening/reclose and tamper-evidence features by forming the laminate from an outer structure joined in face-to-face relation to an inner structure. Score lines are formed in both structures to enable an opening to be formed through the laminate by lifting a flap out of the plane of the laminate. The score line through the outer structure defines a larger opening than the score line through the inner structure, such that a marginal region of the outer structure extends beyond the edge of the opening portion of the inner structure. A pressure-sensitive adhesive is used to re-adhere the marginal region to an underlying surface of the inner structure adjacent the opening through the laminate. The outer score line includes at least one tear portion that is torn through upon initial opening, thus indicating that the package has been at least partially opened.

Avery Dennison in EP 2 323 921 B1 discloses a resealable container that has an easily accessed, yet airtight seal via the use of a tamper evident rupture strip which provides the container or package with improved shelf life for the product contained therein.

None of the prior-art documents uses an adhesive precursor composition that is converted upon request by physical means, such as actinic irradiation, into specific adhesive regions having different specific bond/peel strengths.

AIM OF THE INVENTION

The present invention aims to provide an alternative to the existing packages with built-in opening and reclose feature and to a method for the production of the laminate presenting specific advantages over the above-mentioned prior art.

SUMMARY OF THE INVENTION

The present invention discloses a flexible laminate for forming a reclosable packaging container comprising a built-in opening and reclose feature, said laminate comprising an inner structure and an outer structure, adhesively joined face-to-face, the outer structure forming the outer surface of the container and the inner structure forming the inner surface of the container, the outer structure comprising an outer flap portion delimited by a scoring line through the outer structure, and an inner structure comprising an inner flap portion delimited by a scoring line through the inner structure, the inner score line and the outer score line creating an opening into the container when the flap portions are peeled back, a marginal region of the outer flap portion extending beyond an edge of the inner flap portion and overlying an underlying surface of the inner structure, the inner and outer flap portions being joined in a second adhesive region and a first adhesive region being disposed between the marginal region of the outer flap portion and the underlying surface of the inner structure for attaching and re-attaching, in use, the outer flap portion to the underlying surface, wherein the bond/peel strength of the first adhesive region is smaller than the bond/peel strength of the second adhesive region, the first adhesive region being permanently tacky and wherein the elementary chemical composition of the adhesive in the first adhesive region and the second adhesive region is substantially the same.

Preferred embodiments of the present invention disclose one or more of the following features:

-   -   the bond/peel strength of the second adhesive region is at least         0.5 N/15 mm, preferably 1.0 N/15 mm and more preferably 1.5 N/15         mm, higher than the bond/peel strength of the first adhesive         region, measured according to a T-peel geometry at a speed of         100 mm/min and room temperature;     -   the bond/peel strength of the first adhesive region (2) should         be lower than 1.3 N/15 mm, preferably lower than 1.1 N/15 mm,         more preferably lower than 0.9 N/15 mm and the bond/peel         strength obtained in the second adhesive region should be higher         than 1.5 N/15 mm, preferably higher than 1.6 N/15 mm, more         preferably higher than 1.8 N/15 mm and can be higher than 3.0         N/15 mm where the peel force represents the tear strength of one         of the substrate layers, the values being measured according to         a T-peel geometry at a speed of 100 mm/min and room temperature;     -   the adhesive comprises one or more (meth)acrylate copolymers or         one or more polyurethane resins;     -   one of the inner or outer structures of the laminate comprises         an adhesive-free region adjacent to the first adhesive region to         create an opening-initiation zone;     -   one of the outer or inner structures has a greater affinity for         bonding to the adhesive of the first adhesive region such that         the adhesive remains with one of the outer or inner structures         when the flap portions are peeled back;     -   the outer structure includes a layer that is reverse-printed on         a surface of the layer facing the inner structure;     -   the inner structure includes a barrier layer providing a barrier         against the passage of at least one of moisture and oxygen;     -   the outer structure comprises a layer of polyethylene         terephthalate or oriented polypropylene and the inner structure         comprises:         -   a multilayer web comprising a metallized polymer film,             preferably a metallized oriented polypropylene and a             heat-sealable material or,         -   a heat-sealable multilayer web, preferably a heat-sealable             metallized oriented polypropylene.

The present invention further discloses a reclosable packaging comprising the flexible laminate.

The present invention further discloses a method for making the flexible multilayer laminate, said method comprising the steps of:

-   -   applying a layer of adhesive precursor onto one surface of the         inner or outer structure;     -   activating said adhesive precursor by actinic irradiation and         creating patterns of first and second adhesive regions, the         first adhesive region having a lower bond/peel strength than the         second adhesive region and the first adhesive region being         permanently tacky;     -   scoring the inner and outer structures by a scoring station         before or after adhesively joining the inner structure to the         outer structure face to face to form the laminate, an outer         score line being formed through the thickness of the outer         structure in registration with the outer perimeter of the first         adhesive region, and an inner score line being formed through         the thickness of the inner structure in registration with the         inner perimeter of the first adhesive region.

Preferred embodiments of the method for making the flexible laminate of the present invention disclose at least one or a combination of the following steps:

-   -   the second adhesive region and the first adhesive region are         patterned, and the position of the opening initiation is covered         by a release layer or the position of the opening initiation is         adhesive-free;     -   the adhesive precursor is pattern-converted into the first and         second adhesive regions under the influence of UV irradiation         through a patterned metered monitoring of the absorbed         irradiation;     -   the pattered metered monitoring of the absorbed irradiation is         performed by means of a patterned mask, positioned between the         adhesive precursor and the irradiation source, said mask         comprising transparent and opaque regions;     -   the patterned metered monitoring of the absorbed irradiation is         performed through the patterned addition of one or more         photoinitiators or one or more light stabilizers;     -   activation comprises the radical activation of ethylenically         unsaturated groups or the cationic initiation of cyclic ether         groups;     -   treating one surface of the outer or inner structure with a         corona or flame treatment to increase the bonding affinity with         the first adhesive such that the first adhesive tends to remain         adhered to the treated surface when the opening portions are         peeled back;     -   the dose of actinic irradiation is comprised between 5 to 300         mJ/cm², preferably between 5 to 200 mJ/cm², more preferably         between 10 to 150 mJ/cm².

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of the built-in opening and reclose feature with a first adhesive region surrounding the opening and a release-coating region or adhesive-free region, the permanently tacky adhesive remaining on the inner structure of the laminate after opening.

FIG. 2 is a view of the built-in opening and reclose feature with a first adhesive region and a release-coating region or adhesive-free region on the opening initiation (grasping portion), the permanently tacky adhesive remaining on the outer structure (flap) of the laminate after opening.

FIG. 3 is a view of a standing pouch comprising a built-in opening and reclose feature according to the invention, with the first adhesive region and the release-coating region or adhesive-free region positioned on the opening initiation, the permanently tacky adhesive remaining on the outer structure after opening.

FIG. 4 is a view of a flow pack comprising a built-in opening and reclose feature according to the invention, with the first adhesive region and the release-coating region or adhesive-free region positioned on the opening initiation, the permanently tacky adhesive remaining on the inner structure after opening.

FIGS. 5 and 6 show a tray comprising a built-in opening and reclose arrangement according to the invention on its lid with a first adhesive region and the release-coating region or adhesive-free region on the opening initiation, the permanently tacky adhesive remaining on the outer structure after opening.

FIG. 7 represents a profile view of the built-in opening and reclose feature in open and closed positions.

FIG. 8 represents a side view of the lamination arrangement.

KEY

-   1. Built-in opening and reclose feature -   2. First adhesive region (lower bond/peel strength) comprising the     permanently tacky adhesive -   3. Second adhesive region (higher bond/peel strength) -   4. Release-coating layer or adhesive-free region for the opening     initiation -   5. Scoring line of the outer structure -   6. Scoring line of the inner structure -   7. Opening initiation in deactivated region (dead zone) -   8. Outer structure of the laminate -   9. Inner structure of the laminate -   10. Marginal region -   11. Barrier layer -   12. Release layer applicator (optionally if required) -   13. Adhesive precursor applicator -   14. Oven -   15. Photoinitiator/photoactivator applicator -   16. Absorbance adjuster applicator -   17. Irradiation source -   18. Mask -   19. Scoring station (laser, kiss cutting . . . ) with eye     mark/scoring coordination

DESCRIPTION OF THE INVENTION

The present invention discloses a flexible laminate structure suitable for forming a packaging container having a built-in opening and reclose feature 1, the laminate comprising a two-part structure, namely an outer structure 8 joined in face-to-face relation with an inner structure 9. The adjectives “inner” and “outer” are related to the position in the packaging container, the inner structure 9 being in contact with the content of the packaging container and the outer structure 8 being in contact with the environment. Inner and outer structures can also be named first and second structures of the laminate.

In general, the inner and outer structures are joined by means of adhesives, wherein the adhesive strength of the adhesive used for the reclosable built-in opening is different from the adhesive strength of the adhesive used for the remainder of the flexible laminate structure.

In prior art, the concept of “differential adhesion strength” on various substrates is always expressed as a binary terminology, referring to a “permanent adhesive” and a “pressure-sensitive adhesive”.

In general, a pressure-sensitive adhesive structure is defined as a separable structure without breaking or rupturing any layer when peeling the structure. A permanent adhesived structure on the other hand, is not separable without breaking or rupturing any layer when peeling the structure.

Yet, the terminology “pressure-sensitive adhesive” is jargon, commonly used and accepted in the industrial world, which actually is erroneous since all adhesives are pressure sensitive. The terminology that would have to be used in order to designate the so-called “pressure-sensitive adhesives” is “permanent tacky adhesives” since the latter adequately and properly expresses their characteristics. Such a permanently tacky adhesive can be used for repeatedly de-attaching and attaching different substrates such as an inner structure and an outer structure of a flexible laminate structure.

Likewise, the terminology “permanent adhesive” cannot be considered as an absolute concept; whether an adhesive is permanent or not will depend on various factors such as type of substrate, application method, temperature and ageing among others.

Because the expressions “permanent adhesives” and “pressure-sensitive adhesives” are not totally representative for real life situations and because transition states between both may exist, the present invention uses the terminology “first adhesive” and “second adhesive” wherein the bond/peel strength of the second adhesive is higher than the bond/peel strength of the first adhesive.

Within the context of the present invention, the term “first adhesive” stands for an adhesive with a first bond/peel strength and which is permanently tacky, while the term “second adhesive” stands for an adhesive with a second bond/peel strength, wherein the first bond/peel strength is lower than the second bond/peel strength, the difference between both being at least 0.5 N/15 mm measured according to a T-peel geometry at a speed of 100 mm/min and room temperature and wherein the first adhesive and the second adhesive are both obtained from the conversion of the same adhesive precursor by subjecting said common adhesive precursor to differential actinic irradiation.

The peel strength tests were inspired by ISO 11339, using a T-peel geometry, at room temperature. The tests were performed using an Instron™ tensile machine with a cross-head speed of 100 mm/min. The width of the tested strips was 15 mm, and the results are reported in N/15 mm. The direction of the peeling with regard to the extrusion direction had no influence. The sample is cut perpendicular to the extrusion direction.

With “permanent tacky”, the present invention means that the bond peel/strength after 5 consecutive de-attaching/attaching cycles does not decrease by more than 75%, preferable by not more than 60%, more preferably by not more than 50% or even not more than 40%, of its initial value. It is obvious that the bond/peel strength values obtained in such tests is, for one type of first adhesive, dependent of the time interval between each de-attaching/attaching cycle, the pressure applied for re-attaching the flap, temperature at which the test is performed, the size of the marginal region 10 and the thickness of the first adhesive in the first adhesive region, among others. In the present invention, the flexible laminate is stored at room temperature for the whole test and the test is repeated at intervals of one hour. The pressure for re-attaching the flap is exerted by pushing the thumb and forefinger against each other.

Although the rupture of facing layers largely depends on their tear strength, it is generally admitted, within the context of the present invention, that the bond/peel strength obtained by the first adhesive should be lower than 1.3 N/15 mm, preferably lower than 1.1 N/15 mm, more preferably lower than 0.9 N/15 mm, to avoid rupturing the facing layer.

The second adhesive cannot be used for opening and reclose features. The bond/peel strength obtained by the second adhesive should be higher than 1.50 N/15 mm, preferably higher than 1.6 N/15 mm, more preferably higher than 1.8 N/15 mm, and can be as high as 3.0 N/15 mm, where the peel force represents in fact the tear strength of one of the layers.

Within the context of the present invention, the “adhesive precursor” is converted into the first adhesive with a first bond/peel strength and a second adhesive with a second bond/peel strength by monitoring the absorbed irradiation dose. The absorbed irradiation dose, converting the adhesive precursor into the first adhesive, is lower than the absorbed irradiation dose, converting the adhesive precursor into the second adhesive.

According to the present invention, a “first region” means a region comprising a first adhesive having a first bond/peel strength and a “second region” means a region comprising a second adhesive with a second bond/peel strength, wherein the first region is obtained by patterned monitoring of the irradiation absorbed by the adhesive precursor according to a first pattern and wherein the second region is obtained by patterned monitoring of the irradiation absorbed by the adhesive precursor according to a second pattern, the absorbed irradiation of the adhesive precursor according to the second pattern being higher than the absorbed irradiation according to the first pattern.

Patterned monitoring of the irradiation absorbed by the adhesive precursor may be performed by a patterned monitoring of the irradiation dose, by a patterned contacting of the adhesive precursor with one or more absorbance adjuster(s) or by a patterned contacting of the adhesive precursor with one or more photoinitiators.

At least one of both structures (8, 9) comprises a first adhesive region 2 and a second adhesive region 3 on its surface. The first 2 and the second 3 regions are obtained by subjecting the adhesive precursor to actinic radiation before or after joining both structures (8, 9).

The selective conversion of specific regions comprising the adhesive precursor into the first 2 or second 3 adhesive regions, through one or more reactions activated by actinic irradiation, has the advantage that both types of adhesives never cover each other.

By “one or more reactions activated by irradiation”, the present invention means the reaction of ethylenically unsaturated groups according to a radicalar mechanism or the reaction of cyclic ether groups according to a cationic mechanism.

The inner and outer structures (8, 9) of the laminate include usual lamination structures. The outer structure generally exhibits a printable polymer layer, sometimes associated to a paper layer. Reverse printing is often preferred. Barrier layer 11 such as oriented polyamide (OPA) or ethylene vinyl alcohol copolymer (EVOH), aluminium foils and the like are usual constituents. The inner structure 9 often comprises a polyolefin seal layer, sometimes associated to support layer, among which oriented polymers like OPP, OPA, OPET . . . . Substantially all combinations are possible and well known by those skilled in the art.

The number of constituents of a laminate are mainly governed by their specific function in the laminate, by lamination facilities and by price considerations. Technically, almost all combinations are possible.

A score line, defined here as a line of weakness or a trough cut, is formed in the outer structure (outer score line 5) to define an outer opening portion and an inner line of weakness or a trough cut is formed in the inner structure (inner score line 6) to define an inner opening portion. The outer and inner opening portions are attached to each other in a second adhesive region 3, except in the marginal region 10 that extends beyond the peripheral edge of the inner opening portion between the outer and inner cut or weakening lines, and corresponds to a first pattern defining the first adhesive region (permanent tacky region) 2 to respond to the permanent tackiness feature of the opening and reclosure feature.

The adhesive precursor is applied over the entire surface of the inner or outer structure, except optionally at the location of the opening initiation, and is converted into a second adhesive region 3 according to a second pattern which consists of the entire surface of the inner or outer structure minus the first pattern, where the adhesive precursor is converted into a first adhesive region 2, and minus the release coating pattern or the optional adhesive-free pattern 4 covering the opening initiation 7 and which is provided in order to facilitate the opening of the reclosable flap.

The bond/peel force of the first 2 and the second 3 regions can be tuned on demand by a patterned metered monitoring of absorbed irradiation by the adhesive precursor, for example by means of patterned masking, or through the patterned metered addition of one or more photoinitiators or one or more light stabilizers to the adhesive precursor. The adhesive precursor can even be totally passivized into a dead zone where no adhesion remains at all. Such a zone can be used as opening initiation for the reclosable flap.

As far as the outer and inner opening portions are connected by an adhesive having the highest bond/peel strength in the second adhesive region 3, they can be lifted out of the plane of the built-in opening as a flap, thereby creating an opening through the packaging structure defined by the inner line of weakness (see FIGS. 1 to 6).

After a first opening, the flap created by the connection of the inner and outer portions can be reclosed by adhering the marginal region 10 of the outer opening portion to the underlying portion of the inner structure 9 via the adhesive with the lowest bond/peel strength in the first adhesive region 2. This permanent tacky adhesive in region 2 can be positioned on the outer or the inner structure (8, 9), by increasing the affinity to it of the underlying substrate via a corona treatment for instance. Both positions having their advantages and drawbacks. Positioned on the inner structure 9, the permanent tacky adhesive in region 2 is often rapidly contaminated by the content of the package, such as confectionary articles or biscuits, etc. Positioned on the outer structure 8, the permanent tacky adhesive in region 2 is possibly passivized by finger contact. The choice of the position of the permanent tacky adhesive (lowest bond/peel strength) is therefore conditioned by the content of the packaging and the requirements of the end-user.

The adhesive precursor of the present invention may be applied onto the entire surface of the inner structure 9 or of the outer structure 8 by any suitable coating process known to those of ordinary skill in the art, for example by direct gravure coating, reverse gravure coating, offset gravure coating, smooth roll coating, curtain coating, slot coating, spin coating, screen coating, transfer coating, brush or roller coating, air-knife coating, spray coating and combinations thereof. The direct gravure coating process is preferred.

Prior to the application of the adhesive precursor, the surface can be treated by corona discharge or flame treatment to increase the affinity of the surface to the first adhesive obtained from conversion of the adhesive precursor.

The thickness of a coated adhesive precursor layer, provided in liquid form, prior to crosslinking, can be any thickness that results in the desired properties, as is well understood in the art. Exemplary thicknesses of an uncured, curable (crosslinkable) precursor adhesive layer may be in the range from about 0.1 to about 20 μm, preferably from about 0.5 to about 15 μm, more preferably from about 1 to 10 μm, and most preferably from about 2 to about 8 μm.

After application of the adhesive precursor on the inner structure 9 or the outer structure 8, different degrees of crosslinking are performed according to different patterns, wherein the adhesive precursor according to the first pattern is converted into the first adhesive region 2 and wherein the adhesive precursor according to the second pattern is converted into the second adhesive region 3, the degree of crosslinking of adhesive in the second region 3 being greater than the degree of crosslinking of the adhesive in the first region 2.

In the present invention, the adhesive precursor is converted into adhesives of various bond/peel strength under the influence of actinic irradiation.

Examples of radiation sources are medium and high-pressure mercury vapour lamps, lasers, pulsed lamps (flashlight), halogen lamps and excimer emitters.

Preferably, within the context of the present invention, one or more medium-pressure mercury vapour UV radiators of at least 80 to 250 W/cm and emitting pressure mercury vapour UV radiator(s) is (are) positioned at a distance of from about 5 to 20 cm from the substrate. The irradiating time period preferably is comprised between 0.1 and 10 seconds, more preferably between 0.3 and 5 seconds, most preferably between 0.5 and 2 seconds for having a radiation dose in the range of from 5 to 300 mJ/cm², preferably from 5 to 200 mJ/cm², more preferably from 10 to 150 mJ/cm².

On the other hand, the adhesive precursor can be cured by bombardment with high-energy electron beams (EB) at for instance 150-300 keV. (for the particular case, where the precursor compositions do not comprise photoinitiators).

According to a first embodiment of the method of the present invention, a mask comprising a pattern of transparent regions (second pattern) and opaque regions (first pattern) is provided.

The transparent regions and the opaque regions can comprise a non-random and repeating pattern. The transparent and/or opaque regions can comprise a substantially continuous pattern, a substantially semi-continuous pattern, a pattern formed by a plurality of discrete areas, or any combination thereof.

The mask of the present invention can be made by a process comprising the steps of providing a thin, transparent material of substantially uniform thickness, such as, for example, a transparent film forming a pattern of opaque regions on the material according to the first pattern. The step of forming a pattern of opaque regions can comprise applying ink to selected regions of the thin transparent material.

The mask may have regions of differential opacities for having different degrees of curing upon irradiation. A mask comprising different patterns with different degrees of opacity can be formed in a multi-step process comprising printing a transparent film to form a pattern of opaque regions having a certain initial opacity, and then printing the film a second (third, fourth, etc.) time, as needed, to form a pattern (or patterns) of opaque regions having another opacity (or other opacities), different from the initial opacity (or different from one another). Other methods of forming opaque regions can be used in the present invention, including, without limitation, chemical, electromagnetic, laser, heat, etc.

A method for making the reclosable flap according to a first embodiment of the present invention, comprises the steps of:

-   -   providing an adhesive precursor comprising one or more         photoinitiator(s) and optionally photoactivators, preferably a         liquid adhesive precursor, onto the entire surface of the inner         structure 9 (with the optional exception of the opening         initiation area not covered by the precursor);     -   providing a mask having opaque regions corresponding to the         first pattern and transparent regions corresponding to the         second pattern;     -   positioning the mask between the adhesive precursor and the         irradiation source;     -   crosslinking the adhesive precursor material, wherein the opaque         regions at least partially shield selected regions of the         adhesive precursor from irradiation such that said selected         regions are partially cross-linked to first adhesive,         permanently tacky regions while other regions of the adhesive         precursor, corresponding to the second pattern 2, are         cross-linked to second adhesive regions; and     -   laminating the outer structure 8 to the inner structure 9.

According to a second embodiment of the method of the present invention, the degree of crosslinking of the adhesive precursor, upon irradiation, is controlled by adjusting its specific absorbance, by providing one or more absorbance adjusters, preferably light stabilizers, according to different patterns.

The one or more absorbance adjusters are provided to the adhesive precursor according to a first pattern and optionally according to a second pattern. The concentration of the one or more absorbance adjusters provided according to the first pattern is higher than the concentration of one or more absorbance adjusters provided according to the second pattern. The concentration of the one or more absorbance adjusters corresponding to the second pattern is preferably zero. Upon irradiation, the adhesive precursor comprising absorbance adjuster according to the first pattern is converted into a first adhesive region 2, said region having a lower bond/peel strength and being permanently tacky, while the adhesive precursor, optionally comprising absorbance adjuster according to the second pattern, is converted into second adhesive region 3, said region having a higher bond/peel strength.

The method for making the reclosable flap of the present invention according to the second embodiment, comprises the steps of:

-   -   providing a curable adhesive precursor comprising one or more         photoinitiators and optionally photoactivators, preferably a         liquid adhesive precursor, onto the entire surface of the inner         structure 9; (with the optional exception of the opening         initiation area);     -   providing one or more absorbance adjusters according to the         first pattern on the adhesive precursor;     -   optionally providing one or more absorbance adjusters according         to the second pattern on the adhesive precursor;     -   irradiating the adhesive precursor material; and     -   laminating the outer structure 8 to the inner structure 9.

The one or more absorbance adjusters may be diluted in for example adhesive precursor in order to facilitate the administration of said one or more light stabilizers to the appropriate concentration.

According to a third embodiment of the method of the present invention, the adhesive precursor preferably does not contain any photoinitiators and optional photoactivators in its matrix. Those one or more photoinitiators and optional photoactivators are printed, preferably in different concentrations, concentration 1 and concentration 2, according to different patterns, on the surface of the adhesive precursor.

In general, concentration 1 provided according to pattern 1 is lower than concentration 2 provided according to pattern 2. Optionally concentration 1 equals zero.

Upon irradiation, the adhesive precursor optionally comprising one or more photoinitiators and optional photoactivators according to the first pattern, is converted into a first permanently tacky adhesive region 2, while the adhesive precursor comprising one or more photoinitiators and optional photoactivators according to the second pattern, is converted into a second adhesive region 3.

The method for making the reclosable flap of the present invention according to the third embodiment, comprises the steps of:

-   -   providing a curable adhesive precursor preferably free of         photoinitiators and optional photoactivators, preferably a         liquid adhesive precursor, onto the entire surface of the inner         structure 9; (with the optional exception of the opening         initiation area)     -   contacting said adhesive precursor with one or more         photoinitiators and optional photoactivators according to the         second pattern on the adhesive precursor;     -   optionally contacting said adhesive precursor with one or more         photoinitiators according to the first pattern on the adhesive         precursor;     -   irradiating the adhesive precursor; and     -   laminating the outer structure 8 to the inner structure 9.

The one or more photoinitiators and optional photoactivators may be diluted in for example adhesive precursor in order to facilitate the administration of said one or more photoinitiators and optional photoactivators to the appropriate concentration.

It is obvious for the one skilled in the art that further embodiments of the method of the present invention comprises a combination of two or more of the above embodiments.

The method of the present invention is characterized in that the overall thickness of the first and the second adhesive regions are substantially the same although a difference in thickness over the section of the laminate web can be contemplated to obtain a higher bond/peel strength in the reclosing area (for example 2.5 g/cm² for higher bond/peel strength and 4.5 g/cm² for the permanently tacky reclosing area).

The different embodiments of the present invention may provide a release-coating layer 4, covering the opening initiation 7, pattern applied onto the inner structure according to a third pattern corresponding to the opening initiation 7.

It is obvious that in the different embodiments of the method of the present invention, the adhesive precursor may be applied either on the inner or on the outer structure.

Since the patterned monitoring of the irradiation, absorbed by the adhesive precursor, may be regulated through the addition of different concentrations of photoinitiator and/or absorbance adjuster to region 1 and region 2 respectively and since said photoinitiators and said absorbance adjusters may be added as a masterbatch, the elementary chemical composition of the first adhesive in the first adhesive region (2) and of the second adhesive of the second adhesive region (3) is substantially the same. By substantially the same the present invention means that both adhesives are obtained from the same adhesive precursor with the eventual exception of photoinitiators/absorbance adjusters. The minor differences in elementary chemical composition between both adhesives may originate from the patterned addition of the components required for regulating the absorbed irradiation dose, said patterned addition being intrinsic to the present invention.

When solvent or water-based adhesive precursors are used, drying means such as ovens or infra-red heaters can be used, allowing the applied adhesive precursor to be in good condition for the next manufacture step (lamination or additional application of one or more monomers/oligomers, one or more (photo)initiator(s), one or more absorbance adjuster(s) and/or release-coating).

The inner and the outer structures (8, 9) are preferably supplied from rolls and have substantially the same width. Once laminated face to face, both structures form a laminate that is a continuous web to be supplied to the final packaging station.

One or both of the inner and outer structures (8, 9) or the adhesively assembled laminate are then scored at a scoring station where an outer score line 5 is formed through the thickness of the outer structure 8 in registration with the outer perimeter of the first region 2 and possibly release-coating layer 4 if an opening initiation 7 is present, and an inner score line 6 is formed through the thickness of the inner structure 9 in registration with the inner perimeter of the first region 2. The score lines (5, 6) can be formed by laser scoring, die cutting or kiss cutting, or any other available method well-known in the art. The position of the scoring station, in case of laser scoring, is principally conditioned by the presence or not of a barrier layer that is able to stop or to reflect the laser beam.

To maintain the outer and inner score lines 5 and 6 in registration around the first region 2 and release layer pattern 4 (outer and inner perimeters of both), the scoring operation is synchronized with the advancement of the laminate by means of an optical sensor detecting an eye mark sequence on the laminate, whose location in relation to first adhesive region 2 and release-coating layer 4 pattern is known. Since tolerances are unavoidable, it is preferable to have the first adhesive region (permanently tacking region) going slightly beyond the outer perimeter of the outer score line 5 than having the second region 3 extending over the outer score line, into the marginal region 10 of the reclosable flap.

In case of laser cutting, the depth and width of the score line can be adjusted by regulating the power output of the beam and the residence time of a given spot on the film surface. These parameters are selected in combination with the material to be scored. Some materials are more receptive than others to laser energy—see for instance U.S. Pat. No. 3,909,582 and U.S. Pat. No. 5,158,499 giving extensive information on laser-cutting technology.

Furthermore, various combinations of mechanical and laser scoring are possible. One possibility is for instance to laser-score one side of the laminate and to mechanically cut the other side if one of both structures is not laser-scorable, for instance in the case of a non-absorbing seal layer, such as polyethylene without reflective barrier layer behind.

In the final laminate, the outer opening portion bonded by the adhesive in the second adhesive region 3 to the inner opening portion is peelable from the underlying surface of the inner structure 9 allowing both portions to be peeled back and to create a reclosable opening. The marginal region 10 formed between the outer and inner score lines (5, 6) on the outer opening portion (first permanent tacky adhesive region 2), is re-attachable to an underlying surface of the inner structure 9.

The inner structure 9 of the laminate comprises one or more of a sealant or support layer(s) forming the inner surface of the laminate. Sealant layers are well known in the art and comprise heat-seal material such as heat-seal lacquer, LDPE, HDPE, EVA, polypropylene, polyolefin copolymers in general, ionomers or cold-seal materials.

The inner and the outer structures (8, 9) can also comprise one or more barrier layer(s) known in the art such as metallized polyolefin films, for instance metallized oriented polypropylene (oPP), ethylene vinyl alcohol copolymer (EVOH), oriented polyamide (oPA). Other possibilities are ceramic-coated films like AlOx or SiOx—coated polymer films or aluminium foil.

The outer structure comprises one or more of the following layers:

-   -   oriented polypropylene (oPP, 10-100 μm, preferably 15-40 μm);     -   high-density polyethylene (HDPE, 10-100 μm, preferably 15 to 40         μm);     -   polystyrene (PS, 10-100 μm, preferably 15-40 μm);     -   oriented polyamide (oPA, 10-100 μm, preferably 10-40 μm);     -   polyester such as polyethylene terephthalate (PET, 10-100 μm,         preferably 10 to 40 μm);     -   paper.         The second layer of the outer structure 8 can be printed outside         or reverse-printed.

All the layers of the inner and outer structures (8, 9) can be laminated by means of adhesives or coextruded with possible tie layer if necessary. The methods for all possible combinations are known in the art.

In the lamination process, the outer structure 8 is provided from a supply roll to a print station for printing graphics and/or indicia on it (not shown). This can be achieved by means of a rotogravure printer. In a preferred embodiment of the invention, the outer structure 8 includes a transparent PET layer or oriented polypropylene that is reverse-printed, which means that the inks are applied to the surface of the PET layer, which is subsequently laminated to another structure, the inks being visible through the outer structure by transparency.

The surface of the outer structure 8 can be treated by corona discharge or flame treatment just prior to printing in the print station or even in an earlier production step. The corona treatment is typically used in the art to render the surface more receptive to the inks and to create a privileged affinity to the permanent tacky adhesive to manage the side where the adhesive has to remain after opening the flap (inner or outer layer).

The inner or outer structure is submitted to application stations for adhesive precursor, (photo)initiators, photoactivators, absorbance adjusters, and release coating formulation.

The adhesive precursor of the present invention comprises one or more polymer(s) and/or oligomer(s) comprising one or more reactive sites, one or more monomers comprising one or more reactive sites, one or more tackifiers, optionally one or more (photo)initiators, optionally one or more photoactivators, and additives for example antioxidants, wetting agents, flowing agents and/or any other additive(s) which are known to those skilled in the art.

The one or more polymer(s) and/or oligomer(s) of the present invention comprise a(n) (meth)acrylate-, olefin-, rubber-, silicone-, urethane-, ester-, ether-structure or a combination of them, comprising groups reactable when subjected to actinic irradiation, preferably comprising one or more ethylenically unsaturated group(s), preferably (meth)acrylate groups, and/or one or more cyclic ether groups.

The adhesive precursor preferably used in the present invention comprises a polyurethane resin or polyacrylic resin comprising reactive groups when subjected to actinic irradiation.

Preferably a radiation-curable polyurethane polymer or oligomer having a (meth)acrylate group at its terminal is obtained from a reaction mixture containing one or more polyol(s), one or more polyisocyanate(s) and one or more hydroxyl group-containing (meth)acrylate monomer(s).

Examples of polyols are polyester polyols, polyesteramide polyols, polyamide polyols, polyether polyols, silicon comprising polyols and rubber polyols having a number averaged molecular weight comprised between 500 and 15,000 g/mole, preferably between 1000 and 10,000 g/mole, more preferably between 2,000 and 8,000 g/mole.

Examples of polyester polyols, polyesteramide polyols and polyamide polyols are preferably obtained from saturated or unsaturated polycarboxylic acids and saturated and unsaturated polyhydric alcohols, aminoalcohols, diamines, polyamines and the like. Suitable carboxylic acids for preparing these polyesters include, for example, adipic acid, succinic acid, phthalic acid and the like. Polyhydric alcohols useful in preparing the polyesters include, for example, ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, neopentyl glycol, hexanediol, trimethylolpropane and the like. Aminoalcohols, for example, ethanol amine are used for the synthesis of polyester amide diols, while diamines such as ethylene diamine, hexamethylene diamine ere used for the synthesis op polyamide diols.

Examples of polyether diols are, for example, the condensation products of ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran and the copolymerization, graft or block polymerization products thereof.

Examples of rubber diols are, for example, polybutadiene derived polyol(s); hydrogenated polybutadiene derived difunctional polyol(s); poly(ethylene/butylene) derived difunctional polyol(s); copolymer of butadiene-acrylonitrile derived difunctional polyol(s), or copolymer of styrene-butadiene-styrene derived difunctional polyol(s), or styrene-isoprene-styrene derived difunctional polyol(s), or copolymer of styrene-ethylene/butylene-styrene derived difunctional polyol(s), or copolymer of styrene-ethylene/propylene-styrene derived difunctional polyol(s), noncrystalline polyether glycol(s).

Examples of silicon comprising polyols are hydroxyl-functional silanes and siloxanes.

Examples of polyisocyanates are isophorone diisocyanate; 2,4 toluene diisocyanate; 2,6 toluene diisocyanate; 4,4-diphenylmethane diisocyanate; 4,4′-diphenyldimethane diisocyanate; di- and tetra-alkyldiphenylmethane diisocyanates and the like.

Examples of the hydroxyl group-containing (meth)acrylate monomers are hydroxy C1-10 alkyl(meth)acrylate(s); such as 2-hydroxyethyl(meth)acrylate and 4-hydroxybutyl(meth)acrylate.

The polyurethane polymer comprising at least one functional group, reactable when subjected to actinic irradiation, preferably is characterized by a weight average molecular weight measured by gel permeation chromatography from about 100,000 to about 2,000,000 g/mole, preferably from about 200,000 g/mole to about 1,500,000 g/mole.

Preferably, a radiation curable (meth)acrylic copolymer or oligomer having one or more ethylenically unsaturated group(s) is obtained from reacting a (meth)acrylic copolymer or oligomer comprising epoxy, carboxyl, hydroxyl or isocyanate group(s) with one or more ethylenically unsaturated group containing compound(s) having a functional group that can react with said epoxy, carboxyl, hydroxyl or isocyanate group(s) of said (meth)acrylic copolymer or oligomer. The ethylenically unsaturated acrylic copolymer of the present invention can be prepared accordingly a two-step process.

The (meth)acrylic copolymer or oligomer having epoxy, carboxyl, hydroxyl or isocyanate group(s) is for example obtained from the polymerization of (meth)acrylate alkyl ester having from 2 to 26 carbon atoms in the alkyl group, such as for example ethyl(meth)acrylate, propyl(meth)acrylate, n-butyl(meth)acrylate, isobutyl(meth)acrylate and (meth)acrylic monomers comprising an epoxy group such as glycidyl(meth)acrylate, an acid group such as (meth)acrylic acid an hydroxyl group such as hydroxyethyl(meth)acrylic or an isocyanate group such as 1-(1-isocyanato-1-methylethyl)-4-(1-methylethenyl) benzene.

Optionally, the (meth)acrylic copolymer or oligomer, having epoxy, carboxyl, hydroxyl or isocyanate group(s), comprises one or more ethylenically unsaturated monomer(s) different from (meth)acrylic monomer(s) such as for example styrene, α-methylstyrene, vinyltoluene, acrylonitrile, vinyl acetate, vinyl propionate, acrylamide, vinyl chloride and (meth)acrylic esters having a benzophenone structure capable of being excited by UV irradiation and abstracting a hydrogen radical; typical examples are 4-acryloyloxy benzophenone, 4-acryloyloxyethoxy benzophenone and 4-acryloyloxy-4′-methoxy benzophenone.

The (meth)acrylic copolymer or oligomer having cyclic ether groups is for example obtained from the polymerization of (meth)acrylate alkyl ester having from 2 to 26 carbon atoms in the alkyl group and (meth)acrylic monomers comprising an epoxy group such as glycidyl(meth)acrylate; 3,4-epoxycyclohexylmethyl(meth)acrylate; or 4-hydroxybutylacrylate glycidyl ether and/or meth)acrylic monomers comprising an oxetane group such as 3-oxetanylmethyl(meth)acrylate and 3-(C1-C6 alkyl)-3-oxetanylmethyl(meth)acrylate.

Optionally, the (meth)acrylic copolymer or oligomer, having cyclic ether group(s), comprises one or more ethylenically unsaturated monomer(s) different from (meth)acrylic monomer(s) such as for example styrene, α-methylstyrene, vinyltoluene, acrylonitrile, vinyl acetate, vinyl propionate, acrylamide and vinyl chloride.

The weight average molecular weight of the (meth)acrylic copolymer, having functional groups reactable when subjected to actinic irradiation, is generally approximately 30,000 g/mole or more, or approximately 50,000 g/mole or more, or approximately 50,000 g/mole or more and approximately 1,000,000 g/mole or less, or approximately 500,000 g/mole or less or approximately 500,000 g/mole or less. The value for the weighted average molecular weight in the present disclosure is in terms of polystyrene equivalent, as determined by gel permeation chromatography.

The one or more monomer(s) that may be used in the radiation curable adhesive precursor used in the present invention preferably comprise a polyfunctional (meth)acrylate such as difunctional (meth)acrylates such as ethoxylated bisphenol A di(meth)acrylate; 1,10-decanediol di(meth)acrylate; tripropylene glycol di(meth)acrylate, trifunctional (meth)acrylates such as ethoxylated trimethylolpropane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate and tetrafunctional (meth)acrylates such as ethoxylated pentaerythritol tetra (meth)acrylate and ditrimethylolpropane tetra (meth)acrylate.

Photoinitiators that may be used in the radiation curable adhesive precursor used in the present invention can substantially be any photoinitiator. The usual photoinitiators are the type that generate free radicals or cations when exposed to radiation energy.

Suitable photoinitiators that generate free radicals include, for example, aromatic ketone compounds, such as benzophenones, alkylbenzophenones, Michler's ketone, anthrone halogenated benzophenones.

There are several suitable photoinitiators commercially available from Ciba including Irgacure 184 (1-hydroxy-cyclohexyl-phenyl-ketone), Irgacure 819 (bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide), Irgacure 1850 (a 50/50 mixture of bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentyl-phosphine oxide and 1-hydroxy-cyclohexyl-phenyl-ketone), Irgacure 1700 (a 25/75 mixture of bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentyl-phosphine oxide and 2-hydroxy-2-methyl-1-phenyl-propan-1-one), Irgacure 907 (2-methyl-1 [4-(methylthio)phenyl]-2-morpholonopropan-1-one), Darocur MBF (a phenyl glyoxylic acid methyl ester), Irgacure 2020 Photoinitiator blend (20% by weight of phenylbis(2,3,6-trimethyl benzoyl)phosphine oxide and 80% by weight of 2-hydroxy-2-methyl-1-phenyl-1-propanone) and Darocur 4265 (a 50/50 mixture of bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide and 2-hydroxy-2-methyl-1-phenyl-propan-1-one). The foregoing lists are meant to be illustrative only and are not meant to exclude any suitable photoinitiators.

Photoactivators that can be used in combination with the aforementioned photoinitiators are well-known in the art and are for example chosen from methylamine, tributylamine, methyldiethanolamine, 2-aminoethylethanolamine, allylamine, cyclohexylamine, cyclopentadienylamine, diphenylamine, ditolylamine, trixylylamine, tribenzylamine, n-cyclohexylethyleneimine, piperidine, N-methylpiperazine, 2,2-dimethyl-1,3-bis(3-N-morpholinyl)-propionyloxypropane, and mixtures thereof. Suitable photoinitiators that generate cations upon irradiation are for example an allylsulfonium hexafluorophosphate salt, a sulfonium hexafluorophosphate salt or bis(alkylphenyl)iodonium hexafluorophosphate.

Examples of absorbance adjusters that may be provided to the adhesive precursor of the present invention comprise light stabilizers comprising UV-absorbers such as for example Tinuvin® 400 and Tinuvin® 477, both hydroxyphenyl triazene UV absorbers, hindered amine light stabilizers such as for example Tinuvin® 292 and Tinuvin® 123, dyes and inorganic and organic fillers.

The adhesive precursor of the present invention further comprises one or more tackifiers selected from the group consisting of emulsified rosin, partially decarboxylated rosin, glyceryl esters of polymerised rosin, partially dimerised rosin, natural resins, hydrogenated wood rosin, plasticised hydrogenated rosin, aliphatic and/or cycloaliphatic hydrocarbon resins; aliphatic hydrocarbon resins from petroleum, aromatic petroleum resins, hydrogenated aromatic resins; mixed aromatic/aliphatic resins, ethylene vinyl acetate copolymers, (meth)acrylate (co)polymers, terpene resins, terpene/phenol resins, cumarone/indene resins, rosin esters, pentaerythritol esters and polydicylopentadiene resins, and modified hydrocarbon tackifier resins.

The adhesive precursor of the present invention comprises from about 5% to about 80% by weight, preferably from about 15% to about 65% by weight more preferably from about 20% to about 50% by weight of one or more tackifier(s).

The radiation curable adhesive precursors, preferably used in the present invention, further comprises from 0% to about 10% by weight, preferably from about 0.1% to 5% by weight of one or more photoinitiator(s); from 0.5 to 25% by weight, preferably from 1 to 20% by weight, more preferably from 2 to 15% by weight of one or more monomers; from about 0% to 5% by weight of one or more photoactivator(s), from 0 to 10% by weight, preferably from 0.1 to 8% by weight of one or more absorbance adjusters; from 0% to about 8% of one or more wetting agent(s); from 0% to about 15% of one or more plasticizer(s); from 0% to about 10% of one or more antioxidant(s); from 0% up to about 40% by weight of one or more colorant(s) and from 0% up to about 12% of one or more rheology modifier(s).

The first adhesive region 2 forms viscoelastic bonds that are permanently tacky and adhere under simple finger pressure.

The adhesive precursor and release-coating layer 4 applying stations (12,13) are complemented by drying means such as ovens or infra-red heater for instance, allowing the applied adhesives to be in good condition for the next manufacture step (additional application of photoinitiatiors/photoactivators, light stabilizers, actinic irradiation, lamination).

The flexible laminate of the invention comprising a built-in open and reclose feature made as in the invention provides a tamper-evidence function because it is very difficult to replace the opening portions after initial opening exactly on the same place as before the opening. When the outer layer of the outer structure 8 is printed, in particular if it is reverse printed, it is almost impossible to achieve perfect registration of the printed matter across the score line when reclosing the package. Alternatively, a tamper-evidence function is provided through an interruption of the inner and/or outer score line (no score line at the interruption), so that after initial opening the inner and/or outer structure are partially damaged at said interruption through which the first opening of the flap is clearly visible.

The flexible laminate of the invention not only can be used for flow packs or pouches (FIGS. 3 and 4) but also for lidding of tray or other container (FIGS. 5 and 6). In this manner, the lid includes a built-in reclosable opening.

EXAMPLES

The following illustrative examples are merely meant to exemplify the present invention but are not destined to limit or otherwise define the scope of the present invention.

Examples 1 to 3 correspond to the embodiments as shown in FIG. 8 and were performed under the following conditions:

Duplex Structure Example 1

A structure of a white pigmented, oriented polypropylene film (WTD from Treofan Germany GmbH & Co. KG) is printed by means of solvent containing polyvinylbutyral colors (PVB from Siegwerk Druckfarben AG & Co. KGaA). A protection layer of polyamide (Release lacquer 10-609345-3 of Siegwerk Druckfarben AG & Co. KGaA) is then applied on the printed surface.

Adhesive precursor Duro Tak 5200 (Henkel), comprising photoinitiator, is then applied at a film thickness of 5 μm over the entire surface of the print-free side of the propylene film except for the release coating pattern where release lacquer (Releaselacquer 10-609345-3 of Siegwerk Druckfarben AG & Co. KGaA) is applied. The adhesive precursor is then subjected to irradiation with ultraviolet light emitted by a 160 W/cm medium pressure mercury vapour UV bulb (Fusion UV systems Ltd) with a mask comprising a substantially continuous transparent pattern, metering 40 mJ/cm², wherein at specific locations U-shaped opaque patterns, metering 10 mJ/cm², are provided, placed between the adhesive precursor and the radiation source. The mask, comprising a transparent web comprising opaque patterns, is running at a speed of 80 m/min to the irradiation source, a speed which is synchronized with the one of the polypropylene web comprising the adhesive precursor. The adhesive precursor, upon irradiation according to the transparent pattern of the mask, is converted into the second adhesive region with higher bond/peel strength. The adhesive precursor, upon irradiation according to the U-shaped opaque patterns of the mask, is converted into first adhesive regions with lower bond peel strength and permanent tackiness. After the patterned irradiation, a metallized foamed polypropylene film (QCM from Treofan Germany GmbH & Co. KG) is then adhesive laminated, with the metallized side contacting the adhesive, to create a duplex structure. After laser perforation, the bond/peel strength corresponding to the first adhesive regions is 1.1 N/15 mm, while the bond/peel strength corresponding to the second adhesive region is 1.9 N/15 mm, according to a T-peel geometry at a speed of 100 mm/min and room temperature. On the backside of the metallized foamed polypropylene, a further cold seal (Naturlex Kautschuk Emulsion—Cold seal S 8085 von Sun Chemical) is pattern applied for the cross and longitudinal seal of the future pack (not represented). In a subsequent experiment, the bond/peel strength of the first adhesive regions was measured after consecutive de-attaching/attaching cycles. After five cycles, a 30 to 50% decrease of the original bond/peel strength value was measured.

Example 2

To the oriented polypropylene film structure of example 1, an adhesive precursor Acronal V 215 (BASF) is applied as in example 1.

Irgacure BP (BASF) is applied at 0.16 g/m² over the entire surface of the adhesive precursor except for the U-shaped patterns which upon irradiation will become the first adhesive region and except for the release coating pattern. Upon irradiation, the resulting pattern, comprising Irgacure BP, will be converted into the second adhesive region with higher bond/peel strength. The adhesive precursor comprising Irgacure BP and the U-shaped patterns, free of Irgacure BP, are irradiated as in example 1, wherein the opaque patterns of the mask are synchronized and perfectly coincident with the U-shaped patterns on the adhesion precursor, which are free of Irgacure BP. After the patterned irradiation, a metallized foamed polypropylene film (QCM from Treofan Germany GmbH & Co. KG) is then adhesive laminated, with the metallized side contacting the adhesive, to create a duplex structure. After laser perforation, the bond/peel strength corresponding to the first adhesive regions is 1.0 N/15 mm and permanently tacky, while the bond/peel strength corresponding to the second adhesive region is 1.7 N/15 mm, according to a T-peel geometry at a speed of 100 mm/min and room temperature.

Example 3

To the structure of example 1, an adhesive precursor Duro Tak 4000 (Henkel) is applied as in example 1.

Tinuvin 400 (BASF) is contacted at 0.3 g/m² with the adhesive precursor according to U-shaped patterns, which upon irradiation will become the first adhesive region. The resulting pattern, free of Tinuvin 400, will be converted into the second adhesive region upon irradiation. The adhesive precursor is then subjected to irradiation with ultraviolet light emitted by a 160 W/cm medium pressure mercury vapor UV bulb (Fusion UV systems Ltd) wherein the polypropylene web is running at a speed of 80 m/sec to the irradiation source metering 40 mJ/cm². After the patterned irradiation, a metallized foamed polypropylene film (QCM from Treofan Germany GmbH & Co. KG) is then adhesive laminated, with the metallized side contacting the adhesive, to create a duplex structure. After laser perforation, the bond/peel strength corresponding to the first adhesive regions is 0.9 N/15 mm and permanently tacky, while the bond/peel strength corresponding to the second adhesive region is 1.9 N/15 mm, according to a T-peel geometry at a speed of 100 mm/min and room temperature.

Laser Perforation (ROFIN-BAASEL Lasertech Equipment)

The laser perforation of the duplex structure can performed according to numerous embodiments, dependent on the available laser equipment. Preferred embodiments are:

-   -   cut inline on both sides of the duplex laminate structure;     -   separately cut inline the first and second structures before         both structures are adhesive laminated to a duplex structure;     -   cut inline one of both structures before the adhesive lamination         of both structures followed by the adhesive lamination step and         then by the cut of the second structure.         After laser cut of the duplex structure to create the built-in         opening and reclose feature for the reclosable packaging of the         present invention, the duplex structure is cut into the right         width and wound on rolls with the printed layer oriented         outside.

All examples can additionally be equipped on the duplex structure with a cold seal on specific positions to seal the finished pack. The used cold seal is S 8085 of Sun Chemical (this step is not represented in the figures). 

1-45. (canceled)
 46. A flexible laminate for forming a reclosable packaging container comprising a built-in opening and reclose feature, said laminate comprising an inner structure and an outer structure, adhesively joined face-to-face, the outer structure forming the outer surface of the container and the inner structure forming the inner surface of the container, the outer structure comprising an outer flap portion delimited by a scoring line through the outer structure, and an inner structure comprising an inner flap portion delimited by a scoring line through the inner structure, the inner score line and the outer score line creating an opening into the container when the flap portions are peeled back, a marginal region of the outer flap portion extending beyond an edge of the inner flap portion and overlying an underlying surface of the inner structure, the inner and outer flap portions being joined in a second adhesive region and a first adhesive region being disposed between the marginal region of the outer flap portion and the underlying surface of the inner structure for attaching and re-attaching, in use, the outer flap portion to the underlying surface, wherein the bond/peel strength of the first adhesive region is smaller than the bond/peel strength of the second adhesive region, the first adhesive region being permanently tacky and wherein the elementary chemical composition of the adhesive in the first adhesive region and the second adhesive region is substantially the same.
 47. The flexible laminate of claim 46, wherein the bond/peel strength of the second adhesive region is at least 0.5 N/15 mm higher than the bond/peel strength of the first adhesive region, measured according to a T-peel geometry at a speed of 100 mm/min and room temperature.
 48. The flexible laminate as in claim 46, wherein the bond/peel strength of the first adhesive region is lower than 1.3 N/15 mm, and the bond/peel strength obtained in the second adhesive region is higher than 1.5 N/15 mm, where the peel force represents the tear strength of one of the substrate layers, the values being measured according to a T-peel geometry at a speed of 100 mm/min and room temperature.
 49. The flexible laminate as in claim 46, wherein the adhesive comprises one or more (meth)acrylate copolymers or one or more polyurethane resins.
 50. The flexible laminate as in claim 46, wherein one of the inner or outer structures of the laminate comprises an adhesive-free region adjacent to the first adhesive region to create an opening-initiation zone.
 51. The flexible laminate as in claim 46, wherein one of the outer or inner structures has a greater affinity for bonding to the adhesive of the first adhesive region such that the adhesive remains with one of the outer or inner structures when the flap portions are peeled back.
 52. The flexible laminate as in claim 46, wherein the outer structure includes a layer that is reverse-printed on a surface of the layer facing the inner structure.
 53. The flexible laminate as in claim 46, wherein the inner structure includes a barrier layer providing a barrier against passage of at least one of moisture and oxygen.
 54. The flexible laminate as in claim 46, wherein the outer structure comprises a layer of polyethylene terephthalate or oriented polypropylene and the inner structure comprises: a multi-layer web comprising a metallized polymer film, or, a heat-sealable multilayer web.
 55. A reclosable packaging comprising the flexible laminate as in claim
 46. 56. A method for preparing the flexible laminate according to claim 46, comprising the steps of: applying a layer of adhesive precursor onto one surface of the inner or outer structure; activating said adhesive precursor by actinic irradiation and creating patterns of first and second adhesive region the first adhesive region having a lower bond/peel strength than the second adhesive region and the first adhesive region being permanently tacky; scoring the inner and outer structures by a scoring station before or after adhesively joining the inner structure to the outer structure face to face to form the laminate, an outer score line being formed through the thickness of the outer structure in registration with the outer perimeter of the first adhesive region, and an inner score line being formed through the thickness of the inner structure in registration with the inner perimeter of the first adhesive region.
 57. The method as in claim 56, wherein the second adhesive region and the first adhesive region are patterned, and wherein the position of the opening initiation is covered by a release layer or wherein the position of the opening initiation is adhesive-free.
 58. The method as in claim 56, wherein the adhesive precursor is pattern converted into the first and second adhesive region under the influence of UV irradiation through a patterned metered monitoring of the absorbed irradiation.
 59. The method as in claim 56, wherein the pattered metered monitoring of the absorbed irradiation is performed by means of a patterned mask, positioned between the adhesive precursor and the irradiation source, said mask comprising transparent and opaque regions.
 60. The method as in claim 56, wherein the patterned metered monitoring of the absorbed irradiation is performed through the patterned addition of one or more photoinitiators or one or more light stabilizers.
 61. The method according to claim 56, wherein activation comprises the radical activation of ethylenically unsaturated groups or the cationic initiation of cyclic ether groups.
 62. The method as in claim 56, further comprising the step of treating one surface of the outer or inner structure with a corona or flame treatment to increase the bonding affinity with the first adhesive such that the first adhesive tends to remain adhered to the treated surface when the opening portions are peeled back.
 63. The method as in claim 56, wherein the dose of actinic irradiation is comprised between 5 to 300 mJ/cm².
 64. The flexible laminate of claim 47, wherein the bond/peel strength of the second adhesive region is at least 1.0 N/15 mm higher than the bond/peel strength of the first adhesive region.
 65. The flexible laminate of claim 47, wherein the bond/peel strength of the second adhesive region is at least 1.5 N/15 mm higher than the bond/peel strength of the first adhesive region.
 66. The flexible laminate as in claim 48, wherein the bond/peel strength of the first adhesive region is lower than 1.1 N/15 mm, more preferably lower than 0.9 N/15 mm and the bond/peel strength obtained in the second adhesive region is higher than 1.6 N/15 mm.
 67. The flexible laminate as in claim 48, wherein the bond/peel strength of the first adhesive region is lower than 0.9 N/15 mm and the bond/peel strength obtained in the second adhesive region is higher than 1.8 N/15 mm.
 68. The flexible laminate as in claim 48, wherein the bond/peel strength obtained in the second adhesive region is higher than 3.0 N/15 mm.
 69. The flexible laminate as in claim 46, wherein the outer structure comprises a layer of polyethylene terephthalate or oriented polypropylene and the inner structure comprises: a multi-layer web comprising a metallized polymer film in the form of a metallized oriented polypropylene and a heat-sealable material or, a heat-sealable multilayer web in the form of a heat-sealable metallized oriented polypropylene.
 70. The method as in claim 56, wherein the dose of actinic irradiation is comprised between between 5 to 200 mJ/cm².
 71. The method as in claim 56, wherein the dose of actinic irradiation is comprised between between 10 to 150 mJ/cm². 